共查询到20条相似文献，搜索用时 31 毫秒
1.
E. Hong C. M. Herbert A. M. Yeneneh T. K. Sen 《International Journal of Environmental Science and Technology》2016,13(11):2629-2638
Significant amount of slurry waste is produced from mineral processing plants globally constituting high levels of both kaolin and sand in aqueous suspension. Large quantities of slurry and mine tailings require efficient handling, transportation and storage system. The transportation and treatment of kaolin–sand slurry is dependent on its rheological behaviour which is a function of temperature, total solid concentration and pH. In this study, the effects of total solid concentration, pH and temperature on rheological behaviour of kaolin–sand mixture were investigated. These parameters were varied to analyse the viscosity, yield stress, flow index and shear force requirements of the mixed kaolin–sand suspension as a function of these varying parameters. Experimental rheological investigation conducted on rotational stress-controlled rheometer equipped with Peltier concentric cylinder system showed that the kaolin–sand mixture suspension is shear thickening in nature. The shear stress-rate rheograms for the kaolin–sand suspension can be modelled by the Herschel–Bulkley model with high levels of accuracy for pH range of 4–11, temperature range of 20–50 °C and solid concentration of 5–50 %. Solid concentration of the suspension was found to significantly affect the rheological behaviour of the mixture where higher kaolin–sand slurry concentration resulted in greater viscosity and the trend becoming less predictable for solid concentration greater than 50 % by weight. pH was another factor affecting the rheological behaviour of kaolin–sand slurry. pH of 3 or less resulted in the dramatic increase of viscosity of the suspension possibly due to the isoelectric point of the mixture system found between pH of 3 and 4. 相似文献
2.
Effect of sand grain size and boundary condition on the swelling behavior of bentonite–sand mixtures
Wang Dong-Wei Zhu Cheng Tang Chao-Sheng Li Sheng-Jie Cheng Qing Pan Xiao-Hua Shi Bin 《Acta Geotechnica》2021,16(9):2759-2773
Deep geological repository is a favorable choice for the long-term disposal of nuclear wastes. Bentonite–sand mixtures have been proposed as the potential engineered barrier materials because of their suitable swelling properties and good ability to seal under hydrated repository conditions. To investigate the effects of sand grain size on the engineering performance of bentonite–sand mixtures, we prepare five types of bentonite–sand mixtures by mixing bentonite with sand of varying particle size ranges (0.075–0.25 mm, 0.25–0.5 mm, 0.5–1 mm, 1–2 mm and 2–5 mm, respectively). We carry out sequential oedometer tests under different simulated repository conditions, including constant vertical stress (CVS), constant stiffness (CS) and constant volume (CV) conditions. The microstructural heterogeneity and anisotropy of these soil mixtures are characterized through the quantitative analysis of micro-CT scanning results. Experimental results reveal that both sand grain size and boundary condition significantly influence the swelling of soil mixtures. Under three conditions, the temporal evolutions of swelling stress and strain follow similar trends that they increase faster at the beginning and gradually stabilize afterward. Comparing the ultimate values, swelling strains follow CVS?>?CS?>?CV, while swelling stresses follow CV?>?CS?>?CVS. Under CS boundary conditions, as the stiffness coefficient increases, the swelling pressure increases and the swelling strain decreases. CT results further indicate that mixtures with larger sand inclusions are more structurally heterogeneous and anisotropic, resulting in increased inter-particle friction and collision and a higher energy dissipation during the swelling process. Moreover, the non-uniform distribution of bentonite in local zones would be intensified, which plays an important role in compromising swelling behavior. Therefore, soil samples mixed with larger sand particles present a smaller swelling stress and strain values. This study may guide the choice of engineered barrier materials toward an improved design and assessment of geological repository facilities.
相似文献3.
《Geomechanics and Geoengineering》2013,8(1):69-74
Many remedial measures have been devised to lessen the damage caused by expansive soils. Physical alteration, chemical stabilization, innovative foundation techniques like belled piers, drilled piers, under-reamed piles and granular pile anchors are some of these remedial measures. Mixing a non swelling material such as gravel or sand to expansive soil is one of the methods of physical alteration. This paper presents experimental data on artificially prepared sand-clay mixes. Swell and consolidation characteristics of these artificially prepared sand-clay mixes were studied in one dimensional consolidometer. Fine sand content and fines content in the expansive soil were arbitrarily varied in the investigation. The fines content was varied as 425–300 μm and 150–75 μm, separated from the same expansive soil based on the grain size. Swell potential and swelling pressure decreased with increasing fine sand content but increased with increasing fines content. Coefficient of compressibility, coefficient of volume compressibility and compression index of the samples decreased initially up to a sand content of 15% and thereafter increased at higher sand contents. 相似文献
4.
The energy equation is an expression of the first law of thermodynamics or the law of conservation of energy. According to the first law of thermodynamics, the externally applied work to a system is equal to the sum of dissipation energy and Helmholtz free energy of the system. However, most of the currently available stress–dilatancy relationships are based on the energy equation of Taylor-Cam Clay type, which hypothesizes that the applied plastic work is equal solely to the frictional dissipation energy. The Helmholtz free energy has been completely neglected. Recently, observed from acoustic experiments, it has been recognized that Helmholtz free energy can be caused by deformation mechanisms other than friction between particles. Thus, it is necessary to include additional terms in the energy equation in order to correctly model the stress-dilatancy behavior. This paper addresses the issue regarding the balance of this energy equation. Analyses of experimental results are presented. Specific forms of the frictional energy and Helmholtz free energy are proposed. The proposed energy equation is verified with the experimental data obtained from Silica sand, Ottawa sand, and Nevada sand.
相似文献5.
This paper investigates the fundamental characteristics of shear strength and deformation of crushed oyster shell–sand mixtures
to stimulate recycling of waste oyster shells. Standard penetration tests (SPT) and large-scale direct-shear tests were carried
out with different kinds of dry unit weight and mixing rate of oyster shell–sand mixture. Correlations between N-value, dry unit weight, and friction angle of mixtures were observed from the results of experimental tests, making it possible
to estimate the in situ strength from SPT, and the coefficient of volume compressibility from the confined direct-shear compression
test. These results also make it possible to compute the settlement of oyster shell–sand mixture when used in soft ground
improvement. 相似文献
6.
Acta Geotechnica - The stress–strain response of sand was observed to depend on its material state, i.e., pressure and density. Successful modelling of such state-dependent response of sand... 相似文献
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Simon A. J. Pattison 《Sedimentology》2020,67(1):390-430
Strongly progradational regressive stacks of shallow marine sandstones are ubiquitous in modern and ancient coastal depositional systems. Many ancient examples form prolific hydrocarbon and freshwater reservoirs in the subsurface. One of the best areas in the world to study progradational shallow marine successions is the Campanian Book Cliffs of Utah and Colorado, where the Desert Member to Lower Castlegate Sandstone interval served as a foundational data set for early sequence stratigraphic models. A strongly progradational stack of 17 parasequences comprises the Desert–Castlegate interval. Parasequences are 6·5 to 20·7 m thick. Normally regressive coarsening-upward successions are abundant, as are flat-topped, rooted foreshore sandstones. Conformable facies contacts mark the transition between the laterally adjoining nearshore terrestrial and shallow marine deposits which are genetically, temporally and spatially linked. The width of the shoreface to inner shelf facies belts varies from 4·8 to 19·9 km per parasequence, with a mean of 12·6 km. Solitary tongue shoreline trajectories are all very low to low angle ascending regressive, varying from +0·0004° to +0·171°. Stacked shoreline system trajectories are also dominantly low angle ascending regressive, with only two descending regressive trajectories, one of which intersects the depositional slope. The predominance of ascending regressive shoreline trajectories and normal regression, rarity of high frequency sequence boundaries, regressive surfaces of marine erosion and descending regressive shoreline trajectories, and absence of third-order sequence boundaries, incised valley fill deposits and no prolonged and regionally extensive sediment bypass, all point towards increasing sediment supply as the dominant driver of the Desert–Castlegate stratal architectures, while reduced accommodation (i.e. decreasing tectonic subsidence) played a secondary role. 相似文献
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10.
Ab initio force constants of structural fragments of -quart, Si-O-Si bridge and SiO4 tetrahedron, are calculated by the gradient (force) method for molecules accessible to spectroscopic investigation, disiloxane and tetramethoxysilane respectively. The comparison of theoretical frequencies with experimental ones enables the empirical scaling of quantum chemical force constants. A generalized approach to the inverse vibrational problem in spectroscopy of solids is outlined. It consists of a joint treatment of vibrational spectra and properties of a crystal related to its homogeneous deformation, namely compressibility and elastic constants. The importance of analyzing the microscopic structure of compressibility for testing the force field model is emphasized. The scaled molecular force constants complemented by the force constants of nonbonded O...O interactions at shortest distances after slight empirical correction are found to be sufficient to reproduce all mechanical properties of -quartz accessible to experimental determination. A discussion of results in terms of structure and bonding including the analysis of various versions of a force field model is presented. The calculated shapes of normal coordinates and uniform strains are validated by satisfactory reproduction of IR intensities and piezoelectric constants. 相似文献
11.
State parameter defined using void ratio, e, and the steady-state line has been shown to be effective in predicting the undrained behaviour of sand. However, steady-state
line for sand with fines is dependent on fines content. To overcome this problem, the concept of equivalent granular void
ratio, e*, has been well investigated. However, the conversion from e to e* has been essentially a back-analysis process. A methodology for converting e to e* without the need of a back-analysis process was first presented. The concept of equivalent granular state parameter, ψ*, defined in terms of e*, and equivalent granular steady-state line was then developed. An extensive experimental study was conducted to investigate
whether ψ* can capture the effects of fines content, and thus can be used to correlate undrained behaviour of sand–fines mixtures without
the need of separately considering the effects of fines content. This study suggested that the effective stress path and deviatoric
stress–strain responses in undrained shearing can be correlated with the ψ* value at the start of undrained shearing irrespective of fines content. 相似文献
12.
Brian Fry Richard S. Scalan Patrick L. Parker John Baccus 《Geochimica et cosmochimica acta》1978,42(8):1299-1302
Stable carbon isotope ratios (δ13C) were determined for 31 plant and 16 animal species from a sand dune community on the south Texas coast. Plants and insects had similar δ13C values, forming two distinct groups, while herbivorous rodents formed a third intermediate group. This suggests that insects at the study site are specialists which feed on C3 or C4 plants, while the rodents are generalists, feeding on plants of both groups. 相似文献
13.
Setianto Samingan Agus Yulian Firmana Arifin Snehasis Tripathy Tom Schanz 《Acta Geotechnica》2013,8(2):155-165
This paper presents results of an experimental work to determine a relationship between swelling pressure and suction of heavily compacted bentonite–sand mixtures. For comparison, tests were also carried out on heavily compacted bentonite specimens. A series of swelling pressure tests were performed using multi-step constant-volume method where suction of the specimens tested was reduced in a stepwise manner toward a zero value. The suction reduction was induced using vapor equilibrium and axis-translation techniques. It is shown that compacted specimens did not exhibit any collapse upon suction decrease and exhibited maximum swelling pressures at zero-equilibrium suction. The development of swelling pressure with decreasing suction of the specimens showed threshold suctions below which a further reduction in suction yields an increase in the swelling pressure of the same magnitude. The magnitude of threshold suction was found to be a function of bentonite content in compacted specimens. 相似文献
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15.
Ahmet Apayd?n 《Environmental Earth Sciences》2012,65(1):241-255
This study explains the impact of sand–gravel mining and over-abstraction, and the response of the groundwater system in the
Kazan Plain, Turkey. The plain used to be known for its fresh groundwater potential, valuable agricultural lands and natural
beauty until the 1980s. According to the estimation in 1975, there was 15.5 million m3 annual useable freshwater in the Quaternary sand–gravel aquifer. Groundwater level ranged between 0 and 5 m from the surface
of the plain in the 1970s. Because of the large and deep excavations by the sand–gravel pits during the past 25–30 years,
the aquifer has thinned and removed entirely in some places. In addition, over-abstraction has accelerated the decline of
the groundwater level, particularly in the middle and the upper part of the plain in recent years. As of 2009, about 12% of
the total volume of the aquifer area removed by the pits and groundwater table has been reduced to between 5 and 20 m. The
decline of the water table reaches 15–20 m in the regions where over-abstraction has taken place. To reduce the hazards to
the groundwater system, the sand–gravel pits have to be banned immediately, a reclamation project applied and abstraction
must be reduced. 相似文献
16.
Vertical electrical sounding (VES) is a traditional method of exploration of sand–gravel mix (SGM) deposits. Geophysicists are challenged not only to determine the boundaries of SGM deposits, but also to determine their basic properties, for example, to locate the zones with high gravel contents within SGM deposits or determine the content of clay particles in sands. In order to meet these challenges, it is necessary to use new methods, in particular, the method of induced polarization (IP). This paper presents the results of direct-current VES-IP surveys that were carried out in the territory of Mosalsk district, Kaluga oblast, in 2015. The measurements were made at both known SGM deposits that are under development and new areas under prospecting where drilling has not been performed as yet. The study results show that all SGM deposits are characterized by high values of induced polarization. The complex adjustment of the apparent resistivity and apparent polarizability curves significantly confine the limits of equivalent models when interpreting the data in complex geological situations when sand-and-gravel deposits weakly differ from the host rocks or are superimposed with a thick layer of conducting clay loams. 相似文献
17.
《Geomechanics and Geoengineering》2013,8(1):47-58
The effect of non-plastic fines (silt) on the undrained monotonic response of saturated and isotropically consolidated sand specimens prepared to various measures of their density was studied in detail through various approaches namely gross void ratio approach, relative density approach, sand skeleton void ratio approach, and interfine void ratio approach. Specimens of 50 mm in diameter and 100 mm in height were tested at a rate of loading of 0.6 mm/min for this purpose. The limiting silt content and the relative density of a specimen were found to influence the undrained monotonic response of sand–silt mixtures to a great extent. Undrained monotonic response was observed to be independent of silt content at very high relative densities; however the presence of fines significantly influenced this response of loose to medium dense specimens. Individual and combined analyses of undrained monotonic peak strengths which are closely related to the liquefaction related problems have been done in this paper to assess the variation patterns. 相似文献
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19.
The microstructures of cm-scale displacement faults offsetting unlithified sequences of finely interbedded sands, silts and clays from outcrops in Denmark have been examined. A variety of shear band types are recognised based on their grain-scale deformation mechanism and internal structure. Shear bands in a Jurassic sequence exposed along the coastline of Bornholm are characterised by intense cataclasis of both sand and clay layers. This deformation mechanism is accompanied by extensive grain scale mixing along discrete shear bands to give a fault rock composition that reflects the relative amount of sand and clay within the faulted sequence. In contrast, shear bands at Nr. Lyngby and Jensgaard, both on the Jutland coast, are characterised by granular flow within the sand units. Grain scale mixing is subdued at these locations so that layers maintain their integrity across the shear band to form a layered internal structure of sand, silt and clay smears. In some instances, particularly at Nr. Lyngby, clays have deformed in a brittle manner so that they do not contribute material to the shear band, which is then comprised exclusively of coarser-grained components. The different deformation mechanisms and internal structures of shear bands are thought to be controlled by burial depth at the time of faulting. 相似文献
20.
Property and behaviour of sand–pile interface are crucial to shaft resistance of piles. Dilation or contraction of the interface soil induces change in normal stress, which in turn influences the shear stress mobilised at the interface. Although previous studies have demonstrated this mechanism by laboratory tests and numerical simulations, the interface responses are not analysed systematically in terms of soil state (i.e. density and stress level). The objective of this study is to understand and quantify any increase in normal stress of different pile–soil interfaces when they are subjected to loading and stress relief. Distinct element modelling was carried out. Input parameters and modelling procedure were verified by experimental data from laboratory element tests. Parametric simulations of shearbox tests were conducted under the constant normal stiffness, constant normal load and constant volume boundary conditions. Key parameters including initial normal stress ( $ \sigma_{{{\text{n}}0}}^{\prime } $ ), initial void ratio (e 0), normal stiffness constraining the interface and loading–unloading stress history were investigated. It is shown that mobilised stress ratio ( $ \tau /\sigma_{\text{n}}^{\prime } $ ) and normal stress increment ( $ \Updelta \sigma_{\text{n}}^{\prime } $ ) on a given interface are governed by $ \sigma_{{{\text{n}}0}}^{\prime } $ and e 0. An increase in $ \sigma_{{{\text{n}}0}}^{\prime } $ from 100 to 400 kPa leads to a 30 % reduction in $ \Updelta \sigma_{\text{n}}^{\prime } $ . An increase in e 0 from 0.18 to 0.30 reduces $ \Updelta \sigma_{\text{n}}^{\prime } $ by more than 90 %, and therefore, shaft resistance is much lower for piles in loose sands. A unique relationship between $ \Updelta \sigma_{\text{n}}^{\prime } $ and normal stiffness is established for different soil states. It can be applied to assess the shaft resistance of piles in soils with different densities and subjected to loading and stress relief. Fairly good agreement is obtained between the calculated shaft resistance based on the proposed relationship and the measured results in centrifuge model tests. 相似文献